Network Working Group                                    F. Templin, Ed.
Internet-Draft                              Boeing Research & Technology
Intended status: Informational                            March 03, 2015
Expires: September 4, 2015


            Client Link-Layer Address Option (CLLAO) Updates
                 draft-templin-dhc-cllao-updates-00.txt

Abstract

   RFC6939 specifies a method for DHCPv6 relay agents to insert a Client
   Link Layer Address Option (CLLAO) in a DHCPv6 Relay-Forward message
   as informational material for the DHCPv6 server.  The server in turn
   is not required to echo the CLLAO back in its replies.  In some
   cases, however, the DHCPv6 client may be interested to receive the
   CLLAO, e.g., to determine if there are L2 devices (e.g., L2 proxies)
   that rewrite the link-layer address.  This document discusses updates
   to RFC6939 to allow the server to echo the CLLAO back to the client.

Status of This Memo

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   This Internet-Draft will expire on September 4, 2015.

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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  CLLAOs in Relay-Supplied DHCP Options . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   [RFC6939] specifies a method for DHCPv6 relays[RFC3315] to insert a
   Client Link-Layer Address Option (CLLAO) in a Relay-Forward message.
   This provides a means for a first-hop relay to inform the server of
   the client's link-layer address on the client<->relay link.  However,
   on some links it may be necessary for the client to determine whether
   there is an L2 device on the path to the relay that rewrites the
   link-layer address.

   Asymmetric Extended Route Optimization (AERO) [I-D.templin-aerolink]
   is an example of a "DHCPv6-over-(foo)" link layer where the client's
   link-layer address may be altered by an L2 device on the path.  In
   that case, if the relay inserts a CLLAO and requests the server to
   include the CLLAO in its replies to the client, the client will
   receive the information it needs.  This can be accomplished through
   the application of Relay-Supplied DHCP Options per [RFC6422] as
   described in the following section.

2.  CLLAOs in Relay-Supplied DHCP Options

   When a DHCPv6 relay forwards a DHCPv6 client's messages, it may
   determine that the client requires its own link-layer address to be
   echoed back in the server's reply.  This determination could be
   through, e.g., administrative configuration, an unspecified
   indication from the client, etc.

   When a relay determines that the client requires its link-layer
   address to be echoed back in the server's reply, the relay includes a
   CLLAO in a Relay-Supplied Options option (RSOO) in the Relay-Forward
   message as described in [RFC6422].




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   When the server receives the Relay-Forward message with the RSOO, it
   includes the encapsulated CLLAO in the list of options to return to
   the client.

   When the client receives the server's reply including the CLLAO, it
   can optionally ignore the option as specified in [RFC6939], or parse
   the option to determine if the link-layer address was altered by an
   L2 switching element on the path to the relay.  This latter behavior
   therefore updates [RFC6939].

3.  IANA Considerations

   Per Section 8 of [RFC6422], IANA is instructed to add CLLAO as a
   permitted option in the "Options Permitted in the Relay-Supplied
   Options Option" registry.

4.  Security Considerations

   DHCPv6 authentication [RFC3315] and/or DHCPv6 Security
   [I-D.ietf-dhc-sedhcpv6] SHOULD be used on unmanaged/unsecured links
   where the link-layer switching elements themselves present a man-in-
   the-middle attack threat.

5.  Acknowledgements

   The proposal was widely discussed on the DHC mailing list, where
   valuable insights were gained.  Those mailing list participants are
   acknowledged for their insights.

   Tomek Mrugalski and Bernie Volz provided helpful administrative
   guidance.

6.  References

6.1.  Normative References

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC6422]  Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options", RFC
              6422, December 2011.

   [RFC6939]  Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
              Address Option in DHCPv6", RFC 6939, May 2013.






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6.2.  Informative References

   [I-D.ietf-dhc-sedhcpv6]
              Jiang, S., Shen, S., Zhang, D., and T. Jinmei, "Secure
              DHCPv6", draft-ietf-dhc-sedhcpv6-06 (work in progress),
              February 2015.

   [I-D.templin-aerolink]
              Templin, F., "Transmission of IP Packets over AERO Links",
              draft-templin-aerolink-52 (work in progress), February
              2015.

Author's Address

   Fred L. Templin (editor)
   Boeing Research & Technology
   P.O. Box 3707
   Seattle, WA  98124
   USA

   Email: fltemplin@acm.org






























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